Before you buy a used car, what is it you really need to know? I mean, we do try our best at Autocar and tell you what tyres to kick, which things to tap and what you ought to be worrying about. The thing is, that’s not really enough. Mostly, ‘what to look fors’ can be very deceiving.

What we need is a book. No, let’s be modern: an interweb site. Nope, that won’t do, either. These days it has to be an app - an app that rates a used car’s repairability. Because we really do need to know whether the car we are about to buy is not just easy to live with but also to fix.

Of course, you can just throw money at a problem, but that can prove to be ruinously expensive. I mean, all we need is a graphic of little spanners to explain the level of difficulty of, say, changing a battery.

I’ll use the battery as an example, because of an email I received from an Autocar reader on an unrelated subject. His 2002 Porsche Boxster requires something of a procedure to get access to the battery. That’s because the genius designers at Porsche imprisoned the battery behind an electronically actuated boot release.

Apparently the factory fix if your Boxster won’t start is to attach some jump leads to the fuse box in the passenger compartment. But that doesn’t work if the battery is as flat as a pancake.